CVE-2025-69872: DiskCache Python Library RCE Vulnerability

CVE-2025-69872 Overview

CVE-2025-69872 is an insecure deserialization vulnerability in DiskCache (python-diskcache) through version 5.6.3. The library uses Python's pickle module for serialization by default, which is known to be unsafe when processing untrusted data. An attacker with write access to the cache directory can achieve arbitrary code execution when a victim application reads from the cache.

Critical Impact

This vulnerability enables arbitrary code execution through malicious pickle payloads, potentially allowing complete system compromise when applications process cached data.

Affected Products

• DiskCache (python-diskcache) versions through 5.6.3
• Python applications using DiskCache with default pickle serialization
• Systems where the cache directory has insufficient access controls

Discovery Timeline

• 2026-02-11 - CVE CVE-2025-69872 published to NVD
• 2026-02-12 - Last updated in NVD database

Technical Details for CVE-2025-69872

Vulnerability Analysis

This vulnerability is classified as CWE-94 (Improper Control of Generation of Code) and relates to the inherent dangers of Python's pickle module when used with untrusted input. The DiskCache library stores cached data using pickle serialization by default, which can deserialize arbitrary Python objects. When an attacker gains write access to the cache directory, they can inject malicious pickle payloads that execute arbitrary code upon deserialization.

The attack requires the attacker to have write access to the cache directory used by the DiskCache instance. This could occur through misconfigured permissions, shared hosting environments, or exploitation of other vulnerabilities that grant file system access. Once the malicious payload is placed in the cache, any subsequent read operation by the application triggers code execution with the privileges of the application process.

Root Cause

The root cause is the use of Python's pickle module for default serialization in DiskCache. Python's pickle is not designed to be secure against untrusted or malicious data—it can execute arbitrary code during deserialization. The library's default configuration does not warn users about this security risk or provide safer serialization alternatives out of the box.

Attack Vector

The attack exploits the network-accessible nature of applications using DiskCache combined with the local file system access requirement. An attacker who can write to the cache directory crafts a malicious pickle payload containing embedded code execution primitives (such as using __reduce__ methods). When the victim application subsequently retrieves data from the cache, the pickle module deserializes the payload, triggering the embedded malicious code.

The exploitation mechanism involves crafting a pickle payload that, when deserialized, executes arbitrary system commands. Common techniques include using Python's subprocess module or os.system() through pickle's object reconstruction capabilities. The malicious payload appears as legitimate cached data to the application but contains instructions that execute during the unpickling process.

For detailed technical information about this vulnerability, see the CVE-2025-69872 Disclosure on GitHub.

Detection Methods for CVE-2025-69872

Indicators of Compromise

• Unexpected files or modified timestamps in DiskCache directories
• Unusual process spawning from Python applications using DiskCache
• Suspicious network connections originating from cache-reading processes
• Anomalous system calls during cache read operations

Detection Strategies

• Monitor file system integrity of cache directories for unauthorized modifications
• Implement application-level logging for cache read/write operations
• Deploy endpoint detection to identify pickle deserialization attacks
• Use behavioral analysis to detect unusual code execution patterns from Python processes

Monitoring Recommendations

• Configure alerts for write operations to cache directories from unexpected sources
• Implement process monitoring to detect child processes spawned during deserialization
• Monitor for suspicious imports or module loading during cache operations

How to Mitigate CVE-2025-69872

Immediate Actions Required

• Restrict file system permissions on cache directories to prevent unauthorized write access
• Audit applications using python-diskcache for potential exposure
• Consider implementing a custom serializer using JSON or other safe formats
• Isolate applications using DiskCache in sandboxed environments

Patch Information

As of the last update on 2026-02-12, users should monitor the python-diskcache GitHub repository for security patches or configuration options to use safer serialization methods. Consider upgrading to newer versions that may address this vulnerability or provide secure serialization alternatives.

Workarounds

• Configure DiskCache to use a custom serializer that does not use pickle (such as JSON for simple data types)
• Implement strict access controls on cache directories to prevent unauthorized write access
• Deploy DiskCache instances in isolated environments with minimal privileges
• Consider using alternative caching libraries that provide secure-by-default serialization

# Configuration example - Restrict cache directory permissions
chmod 700 /path/to/diskcache/directory
chown application_user:application_group /path/to/diskcache/directory

# Verify no unexpected files in cache directory
find /path/to/diskcache/directory -type f -mtime -1 -ls